1. Technical Field
The present invention relates to a high-precision machine tool platform, and more particularly, to an oblique-driven platform structure.
2. Description of Related Art
With the development of industry and technology, every industrial product now progresses toward micro and concise. Hence, a new developed topic on micro/meso-scale manufacturing technology will be critical to manufacturing technology, wherein the micro/meso-scale drilling technology can be applied to national defense, aerial transportations, electronic devices, optical devices, communication, and bio-medical industry, particularly to high speed communication micro optical devices, micro-actuator and micro-sensor on vehicle and medical tools, micro-nozzle on high temperature jet engine, and micro fuel cell.
Currently, the micro/meso-scale drilling technology is mostly achieved by using multi-axles machine tool, wherein the multi-axles machine tool is belong to serial connected mechanism, and its driving way is carried out though the cooperation of hydrostatic linear guide ways and linear motors. The multi-axles machine tool includes the advantages of rapid operation and no back clearance; however, it also has the drawbacks of difficult to assembly and high equipment cost. In addition, the serial connected mechanism needs a huge working area because it has the main structure of cantilever. So that, the serial connected mechanism may deform or have displacement due to external loading or its weight. Moreover, only the conventional servo system of serial connected mechanism of higher precision may achieve the precision of sub-micron or even nano-meter scaled.
Accordingly, the manufacturers of machine tools study and then propose a toggle-type positioning platform, which is able to transform the displacement of a screw to the feed rate of a work platform by using a trigonometric relation; besides, the toggle-type positioning platform can meet the requirement of high resolution and high precision without using any high-level servo mechanisms (i.e., the linear motors and the hydrostatic linear guide ways).
Please refer to FIG. 1, which illustrates a top view of the toggle-type positioning platform. As shown in FIG. 1, the toggle-type positioning platform 100′ includes: a first platform 112′, a motor 120′, a screw 130′, a second platform 114′, and a connecting rod 140′. The motor 120′, the screw 130′ and the second platform 114′ are disposed on the first platform 112′, and the second platform 114′ can motion on the first platform 112′ along a predicted way d′ back and forth, wherein an included angle θ2′ is formed between the extension direction of the predicted way d′ and the screw 130′, and an included angle θ1′ is formed between the connecting rod 140′ and the screw 130′.
The connecting rod 140′ is located between the first platform 112′ and the second platform 114′, and simultaneously connecting to the second platform 114′ and the screw 130′, wherein the connecting rod 140′ is indirectly connected with the screw 130′ through a sliding block 141′. Therefore, when the screw 130′ rotates, the connecting rod 140′ would be driven to move and further drive the second platform 114′ to motion along the predicted way d′. As shown in FIG. 1, the first platform 112′ has a guide groove 160′; besides, a ball bearing 180′ is disposed in the guide groove 160′ and located between the first platform 112′ and the second platform 114′. Therefore, the ball bearing 180′ would move along the guide groove 160′ when the second platform 114′ moves along the predicted way d′, and this way is able to steady the motion of the second platform 114′.
Furthermore, for increasing the stability of the second platform 114′, a guide rail 170′ is added into the first platform 112′, and a roller bearing 190′ is disposed in the guide rail 170′ and located between the first platform 112′ and the second platform 114′. Thus, the roller bearing 189′ would move along the guide rail 170′ when the second platform 114′ moves along the predicted way d′, and this way is able to increase the stability of the second platform 114′.
Please refer to FIG. 2, there is shown a schematic motion diagram of a connecting rod of the toggle-type positioning platform. As shown in FIG. 2, X′ represents the position of the sliding block 114′ on the stroke position of the connecting rod 140′ on the screw 130′, H′ represents the displacement resolution of the second platform 114′, and L′ represents the length of the connecting rod 140′. Because the stroke position X′, the displacement resolution of platform H′ and the length L′ construct a geometric triangle, a trigonometric relation is formed between the stroke position X′, the displacement resolution of platform H′ and the length L′. Therefore, through the trigonometric relation, it is able to calculate the displacement resolution of platform H′ easily.
By above descriptions, it can know that the toggle-type positioning platform 100′ has the advantages of easy to calculate the displacement resolution of platform H′ and high platform stability. However, the toggle-type positioning platform 100′ is still not perfect and includes some drawbacks. As shown in FIG. 2, when the connecting rod 140′ moves with the motion of the second platform 114′, the included angle θ1 is changed from θ1a′ to θ1a′ when the connecting rod 140′ moves from the stroke position Xa′ to the stroke position Xb′. The change of the included angle θ1 means that the trigonometric relation between the stroke position X′, the displacement resolution of platform H′ and the length L′ is changed, therefore the value of the displacement resolution of platform H′ calculated through the trigonometric relation between the stroke position X′, the displacement resolution of platform H′ and the length L′ is also be changed.
Please continuously refer to FIG. 2, and simultaneously refer to FIG. 3, which illustrates a curve plot diagram of the screw stroke position and the platform displacement resolution. In the toggle-type positioning platform 100′, the minimum resolution of the stroke position X′ is dominated by the motor 120′ and the screw 130′, and the minimum stroke position resolution would affect the minimum resolution of the displacement resolution of platform H′. Herein, the motor 120′ and the screw 130′ used for contributing the data shown in FIG. 3 provide the minimum stroke position resolution of 1 μm, and the minimum resolution of the displacement resolution of platform H′ can reach nano-meter level by using the toggle-type positioning platform 100′. Moreover, through the data shown in FIG. 3, it can also find that the value of the displacement resolution of platform H′ is changed with the increase of the stroke position X′ of the screw 130′. It means that the displacement resolution of platform H′ is not a constant in the toggle-type positioning platform 100′. More clearly to explain that, the displacement resolution of platform H′ is getting worse with the increase of the stroke position X′ of the screw 130′.
Accordingly, in view of the conventional multi-axles machine tools and the toggle-type positioning platform still have some shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided an oblique-driven platform structure.